1. Field of the Invention
The present invention relates to a method of manufacturing books or brochures with a book block of printed sheets which are thread-stitched at the side of the fold. The method includes successively and in a predetermined sequence supplying the printed sheets spread in the middle and with the side portions thereof directed downwardly to a stitching saddle which interacts with a stitching device arranged at a right angle relative to the fold of the printed sheets. The printed sheets are positioned on the stitching saddle in accordance with the stitching position and are subsequently transferred to the stitching device for sewing the printed sheets into book blocks.
2. Description of the Related Art
Methods of the above-described type are carried out, inter alia, with thread stitching machines of the type "Inventa" of Muller Martini Buchbindesysteme AG.
In accordance with these methods, the printed sheets are initially separated in a predetermined sequence and collected in loose stacks, are transferred to a conveying unit, are opened in the middle on the conveying path and are transferred astride onto an intermediate conveyor connected to the stitching saddle of a stitching device. At the conveying end of the intermediate conveyor, each printed sheet is grasped by a feeding unit at the forward edge of the sheet and is moved against a position stop located on the left hand side on the stitching saddle.
This is carried out in the case of printed sheets of small sizes as well as of large sizes. In other words, the shortest printed sheets on the intermediate conveyor as well as the longest printed sheets travel the same distance from the intermediate conveyor to the position stop on the stitching saddle. The speed V is also the same for all printed sheets and the stitching device sews approximately two hundred printed sheets per minute, i.e., more than three printed sheets per second.
The transfer of the printed sheets from the intermediate conveyor to the stitching saddle requires, for increasing the spacing, a brief acceleration of the printed sheets grasped by the intermediate conveyor and, thus, the transfer is not without problems.
Consequently, printed sheets which have a shorter backfold length and the attendant higher lability than the greatest size that can be processed, are moved over an excessively long distance to the position stop, so that the reliability of a correct transfer is also difficult to achieve.